I think it's because Enzo's not a born psycho but a raised psycho. Sometimes it seems like he's working too hard to prove his madness, lol... uh well, not just his madness but almost everything about him (⌒▽⌒) just look at his pose!
Chill (〜￣△￣)〜
To me, he does seem more like psychopath (born) in anti-social disorder spectrum than sociopath (developed), and psychopathy stayed in wrong lane because of the upbringing taught him wrong things... So he originally had it at some level, and that is the way he learned to use it. Not that it fully developed later.
Because even with psychopaths, it does matter how you grow up.
But armchair diagnosing comic book characters is impossible task anyway, especially characters that barely have had one series. So I can't be too serious about it. xD
Well, everyone has a bit of it in them, don't they?
And if we consider his grandpa, then genetic is not working in his favor, well, not with his looks, lol. But again, we have to assume his father disappointed his grandfather by staying sane/not getting involved with his crime syndicate, so my bet is on him being a raised psycho ╮(￣▽￣)╭
Enzo takes himself way too seriously lol he needs to chill out